Police believe Thongpoon Chanachan fell asleep behind the wheel and died instantly in the collision.
He was taking the workers from Bangkok to renew their visa in Tak.
Rescue workers had to use heavy equipment to extract two injured passengers from the wreckage.
The other slightly injured passengers told police that they left Bangkok at 10.30pm on Wednesday to renew their visa in Tak's Mae Sot district.
Police initially suspect that the van driver dozed off behind wheel due to exhaustion from a long drive.